Method of cracking hydrocarbons



July 23, 1929. T. MIDGLEY. JR

METHOD OF CRACKING HYDROCARBONS Fiied May 5, 1923 INLET PIPE CONDENSER Patented July 23, 1929.

UNITED STATES PATENT OFFICE.

THOMAS MIDGLEY, JR, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, T GENERAL MOTORS CORPORATION, OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

METHOD OF CRACKING HYDROCARBONS.

Application filed May 5, 1923. Serial No. 636,892.

This invention relates to modes of cracking the heavier hydrocarbons, and its principal objects are to increase the yield of aromati hydrocarbons and to employ a nonhydrogenating cracking catalyst.

In the accompanying drawing, the figure is a diagrammatic view, partly in section, of an apparatus for carrying out my process of cracking hydrocarbon oils.

In this figure, 1 is a cracking chamber which, for small production, may be made of iron tubing thirty-five inches long and two inches in diameter. 2 is an inlet pipe having a valve 3, and 4 is an outlet pipe leading 15 from the cracking chamber to a condensing coil 5 located in a cooling chamber 6. This coil may be cooled by running water or ice.

The cracking chamber 1 is enclosed in a heating jacket having an electrical heating 2o coil divided into sections 7 and 8, each of which may be connected by wires 9 and switch 10 with a 110 volt line 1101' a 220 volt line 12. An insulating cover 13 surrounds the heating coil.

The cracking chamber vis substantially filled with pieces 14 of pumice stone or other porous material, the size of the pieces in the apparatus illustrated being" uniform and about one half inch in diameter. A free 30 space is provided at the top of the chamber above the level of the pumice stone.

In one method of cracking oils, the heated vaporized oil is brought into contact with a catalytic substance which presents free selenium to the oil vapor. This substance may be prepared by fusing iron and solenium in such proportionate quantities that free selenium ispresent in the alloy. 10% of selenium above molecular proportions has been found satisfactory for the purpose. The iron serves as a base for the selenium and tends to keep the vapor from carrying the selenium out of the cracking chamber. The cooled alloy is ground up until it will pass through a 100 mesh sieve, mixed with kerosene or other vehicle and'the alloy is deposited in the pores of the pumice stone by dipping and agitating the latter in the alloy-kerosene mixture.

The pumice stone, impregnated with from to of a pound of the alloy, is placed in the cracking chamber, the control switches are thrown to connect the coils 7 and 8 of the heating jacket with the 220 volt system to bring the temperature of the chamber the presence of the free selenium more readily than when using 700 C. and even higher temperatures without pressure, and yields a high percentage of aromatic hydrocarbons. Yields as high as 40% aromatic hydrocarbons and 24% gasoline have been obtained.

These vapors are collected from the condenser coil 5 as liquids, a very small percentage of fixed gases, probably of the methane and low boiling olefine series, coming through the coil.

This process may be varied by employing as a base for the selenium another metal such as nickel, cobalt, or lead, and tellurium may be used in place of the selenium. The catalytic substances formed with any of these bases or containing tellurium may be prepared and employed in'the process in the same manner as the ferrous selenide. The selenium catalyst is preferred to the tellurium catalyst because it is cheaper and the yields obtained are higheiz .Temperatures from 400 C. to 600 C. may be employed but the best results have been obtained at 500 C. The process may be operated at above 600 C. but largcryiclds of fixed gases are obtained and to avoid this, the lower temperatures are employed. Pressure may be used but it has been found that the product contains a relatively large content of olefines without a proportionate increase in the aromatic hydrocarbons.

An increase in the rate of feeding the oil to the cracking chamber generallydecreases the proportionate quantity of oil cracked.

lVhile the process has been described in the cracking of kerosene, it may be employed with other of the heavy hydrocarbon oils.

The catalysts function in the process as described as nonhydrogenating catalysts, i. e., a catalyst which does not hydrogenate unsaturated organic compounds. Compounds which present free selenium or telwhich comprises combining a catalyst of the selenium type with a metal base in proportion to present the catalyst on the surface of the base, and cracking a vaporized hydrocarbon oil by contact with the catalyst.

4. A process as described in claim 1 in which vapours of the hydrocarbon oil are heated to atleast 400 C. and While so heated are brought into contact With the catalyst.

In testimony whereof I hereto afiix my signature.

THOMAS MIDGLEY, JR. 

